To define coronary angiographic characteristics of patients experiencing early primary ventricular fibrillation (VF) in the acute phase of myocardial infarction we studied 266 consecutive patients without clinical evidence of heart failure. Twenty-six patients (group 1) experienced early (< 12 h from the onset of symptoms of myocardial infarction) primary VF whereas 240 patients (group 2) with the same clinical characteristics served as an appropriately matched cohort. All patients were catheterized before or soon after hospital discharge (1 to 8 weeks after the acute event). There was no significant difference in left ventricular ejection fraction between the two groups of patients (39.6 +/- 6% vs 36.9 +/- 8%, P = ns). Patients with early VF had a significantly greater number of diseased vessels than those without VF (3.38 +/- 1.05 vs 2.03 +/- 1.25, P < 0.001) and a higher coronary arteriographic Gensini score (29.31 +/- 4.80 vs 20.16 +/- 4.14, P < 0.001). The left anterior descending coronary artery was identified as the infarct-related vessel in 53.6% of group 1 vs 44.5% of group 2 patients (P < 0.05). The mean maximal serum creatine kinase values were not significantly different (1897 +/- 1062 vs 1426 +/- 839 IU.l-1, P = ns) between the two groups. These data indicate that patients with early primary VF in the setting of acute myocardial infarction may have more extensive coronary artery disease than similar patients without VF. A worse prognosis could be anticipated for these patients on the basis of worse coronary anatomy.(ABSTRACT TRUNCATED AT 250 WORDS)